\begin{tikzpicture}[scale=0.5]
    \tkzDefPoints{0/0/A, 10/0/B, 5/0/D, 2.5/0/E}
    \tkzDefLine[perpendicular=through E](A,B)  \tkzGetPoint{x}
    \tkzCalcLength(A,D)  \tkzGetLength{ad}
    \tkzInterLC[R](E,x)(D,\ad)  \tkzGetFirstPoint{C}
    \tkzDrawPolygon(A,B,C)
    \tkzDrawSegments(C,D  C,E)
    \tkzMarkRightAngle[size=0.4](A,C,B)
    \tkzMarkRightAngle[size=0.4](C,E,A)
    \tkzLabelPoints[left](A)
    \tkzLabelPoints[right](B)
    \tkzLabelPoints[above](C)
    \tkzLabelPoints[below](D,E)
\end{tikzpicture}

